Light sensitive paper and method of treating same



Patented Sept. 13, 1938 PATENT OFFICE LIGHT SENSITIVE PAPER AND METHOD OF TREATING SAME- Clyde A. Crowley and George H. Goodyear, Chicago, Ill., assignors to The Huey Company, Chicago, 111., a corporation of Illinois No Drawing. Application April 29,1938, Serial No. 205,008

3 Claims.

Our invention relates to light-sensitive paper and particularly relates to a novel coating for blue print paper and to a chemical compound adapted for "use in the preparation thereof.

This application is a continuation in part of our application, Serial No. 172,962, filed Nov. 5, 1937, which in turn is a continuation'in part of our application, Serial No. 139,950, filed' April 30, 1937, now issued as Patent No. 2,113,423.

A developer of the type intended for use in the described relation is disclosed in our U. S. Patent ing compound that is relatively slow in action and Y which does not produce bright or intense blue 35 color-without bleeding and the resultant partial obliteration of the white lines. An object of our invention is, therefore, to provide a perfectly stable coating, one that operates to completely eliminate bleeding in development and one in to which an intense blue is present in the final product, and a paper which prints at greater speed than products heretofore known.

The improvement is brought about by the use of a novel coating containing some of the usual 35 components, but in which a substance that acts as a catalyzer to accomplish the needed results is incorporated. The catalytic agents which'we have discovered are the cesium salts.

In practice, we prefer cesium mono-nitrate for those applications where the cost of this chemical in the sensitizer canbe commerciallytolerated.

Cesium mono-nitrate appears to be the most desirable of the catalysts investigated, probably by virtue of the fact that under certain conditions 45 which may prevail during the process of development with our special predeveloping solution described in our Patent No. 2,093,42l,the valence of the cesium may be increased and the polyvalent ions resulting, act as secondary; catalysts in connection with the special development process. Theoretically, the greater eflectiveness oi cesium mono-nitrate may be ascribed to two factors. Due to the heavier molecular weight of cesium, its absorption spectrum lies in a region of longer wave lengths. Most of the longer wave 5 lengths of light falling on blue print paper during exposure are not effective because they are not absorbed. 'I'hepresence of the cesium mononitrate, therefore, makes eiiective a greater proportion ofthe light which falls on the paper.

The second factor making cesium more eflective is its polyvalent nature. The other alkali metals above cesium in the periodicv table do not exhibit this property. The known higher valen= cies indicate that electrons are lost with greater ease; that is, less energy is required to cause a reaction. This again makes longer wave lengths of light effective since less energy is associated per quantum of radiation of long wave length. Again, the presence of cesium mono-nitrate makes a greater proportion of the light falling upon the paper efiective.

The stabilizing influence of the catalyst on the sensitizing solution is not impaired by this probable change, and it is to be observed that regard-'- less of whether this preferred catalyst or one of the catalysts disclosed in other pending applications is present, the sensitized layer is rendered definitely more stable with respect to the final keeping property of the paper, and with respect to that characteristic of the sensitized layer which makes possible the development of an in tense blue background; white lines, and freedom from bleeding. We do not wish to restrict the use of the cata- .35 lysts disclosed'in this application to sensitized -blue print papers which are to be developed exclusively by the process disclosed in our U. S.

to formulate sensitizing solutions particularly adapted to take advantage of the catalytic reactions induced by this substance.

Satisfactory formulas follow:

1. Potassium oxalatefl oz 12 2. Oxalic acid oz 1 3. Cesium mono-nitrate oz 6 4. Ferric ammonium oxalate lbs' 8 5. Potassium ferricyanide oz 6 6. Water, to bring the solution to B.

This formula makes approximately five' (5) gallons.

1. Potassium carbonate oz 10 2. Oxalic acid oz 8 3. Cesium acid tartrate oz 8 4. Ferric ammonium oxalate lbs 10 5. Potassium ferricyanide oz 5 6. Water, to bring the solution to 15 B.

This formula makes approximately five (5) gallons.

A paper sensitized with the above solutions will not produce good prints when developed in the ordinary manner, due' to their low potassium ferricyanide content. If a special predeveloper of the type described in our U. S. Patent No. 2,093,421 and hereinafter described is not used, the color is not sufficiently deep.

However, when a paper coated with the above types of sensitizers are treated with this special type of predeveloper, an exceptionally fine print will result. For example, the so-coated sheet should be developed in a solution such as the following and then be washed and treated with an oxidizing solution and rinsed.

1. Potassium carbonate oz 10' 2. Oxalic acid oz 8.5 3. Disodium phosphate (NazI-IPO4.12H2O) oz 22 4. Glucose oz 5.5 5. Potassium ferrocyanide lbs 7 6. Sodium bisulphite oz 13.5 '7. Water, to make gals 5 A number of other satisfactory predevelopersolutions are disclosed in our said U. S. Patent No. 2,093,421. Another satisfactory solution is as follows:

1. Potassium carbonate; oz- 11 2. Oxalic acid oz 9.5 3. Disodium phosphate (Na2I-IPO4.12HzO) oz 24 4. Sucrose oz 8 5. Potassium ferrocyanide "lbs" 8 6. Sodium bisulphite oz 12 7. Water, to make gals 5 When the exposed paper is washed in-a solution such as above defined, the excess of ferrous iron in the exposed portions reacts with the ferroyanide of the predeveloping solution to form ferro-ferrocyanide. The concentration of the ferrocyanide ion in the developer is great enough so that no ferrous iron has the opportunity to wash or bleed due to the insolubility of ferrous ferrocyanide.

The exposed paper is then given the customary water wash, bichromate wash and water rinse.

when in use, this predeveloper gives better results if the oxidation of the ferrocyanide is inhibited by the presence of a reducing agent, but

this reducing agent must not be strong enough to reduce the iron in the ferric complex on the paper. 'In practice, sodium bisulphite has been found satisfactory.

A further improvement in the brilliance of the print is achieved by decreasing the particle size of the pigment on the paper. This is done by means of aliphatic polyhydroxyl compounds, f phatic aldehydes and aliphatic ketones incorporated in the predeveloper which will not'react with iron salts to form insoluble reaction products. In practice,. various sugars are satisfactory.

In order to obtain good whites with the ferrocyanide predeveloper, it is necessary to buffer the acid concentration rather carefully. Any of the common acid buffers are satisfactory, provided they do not have too powerful oxidizing or reducing properties. In use are mixtures of potassium oxalate,'potassium acid oxalate and oxalic acid or mixtures of sodium acid phosphate and'oxalic acid.

It will be noted that the catalyst constitutes a small but definite component in the sensitizers disclosed.

Although the specific chemical or chemicalphysical mechanism is not understood. it is believed that the action is catalytic.. This catalyst may be incorporated with the known type of sensitizing solution as follows:

Grams I. 1. Cesium mono-nitrate 3 2. Citric acid 6 3. Potassium oxalate 6 4. Ferric ammonum oxalate 39 5. Potassium ferricyanide 9.5 6. Water--to make 250 cc.

II. 1. Cesium sulphate 3 2. Potassium oxalate 6 3. Citric acid 6 4. Ferric ammonium oxalate 40 r 5. Potassium ferricyanide; 7.5 6. Water-to make 250 cc.

This formula is for development in the customary manner involving washing and treatnient with an oxidizing agent.

In all cases the inclusion of the catalyst improves the speed and the blue color, improves the ease of washing the paper and stabilizes the Y sensitizing solution against deterioration during storage, as well as stabilizing the paper thus coated against rapid spoiling under normal or adverse atmospheric conditions.

We claim:

1. The method of making blue prints whichconsists in coating a. paper with a solution comprising a light-reducible ferric complex, a ferricyanide salt and a cesium salt, then exposing parts of said paper to light and then develop-v ing said paper.

2. The method of making blue prints which consists in coating 8. paper with a solution comprising a light-reducible ferric complex, a ferricyanide salt and a cesium salt, then exposing parts of said paper to light and then treating said paper in a predeveloper comprising an acid reacting water solution of a ferricyanide.

3. A coating for blue print paper comprising a light-reducible ferric complex, a ferricynnide salt and a cesium salt.

CLYDE A. CROWLEY. GEORGE H. GOODYEAR. 

